Parallel shuttle types of automatic pallet changers for alternately changing two pallets located parallel to each other are known, for example, from JP-A-58-71045, in which hooks adapted to engage pallets are moved in a reciprocating motion along pallet-placing rails by means of chain mechanisms, and also from JP-A-62-166942, in which hooks adapted to engage pallets are provided at the ends of two hydraulic cylinders, which are alternately actuated to perform operations of changing the pallets.
However, in the above-described conventional devices, the operations of changing the pallets are performed by a plurality of (for example, two) actuators arranged independently of each other with respect to the respective pallets. Thus, the conventional devices had disadvantages in that the efficiency of operations of the actuators is lower, since, while one of the actuators is being operated, the other is stopped.
Furthermore, the devices had a further disadvantage in that the need of arranging the plurality of actuators made the driving system complicated and larger-sized.